A light source driving circuit for powering a first light source and a second light source by a DC voltage includes a first current regulator, a second current regulator and a controller. The first current regulator controls a first switch coupled to the first light source based on a first current reference and a first sensing signal. The second current regulator controls a second switch coupled to the second light source based on a second current reference and a second sensing signal. The controller regulates the current through the first light source and the current through the second light source by controlling the first current regulator and the second current regulator. If the DC voltage is within a first range, then the controller turns on the first light source. If the DC voltage is within a second range, then the controller turns on the first light source and the second light source.